Developed specifically for science, engineering, and financial computations,
Intel™ Math Kernel Library (MKL) is a set of threaded and vectorized math
routines that work to accelerate various math functions and applications.
Anaconda has packaged MKL-powered binary versions of some of the most popular
numerical/scientific Python libraries into MKL Optimizations for improved
performance.

MKL Optimizations includes:

Speed-boosted NumPy, SciPy, scikit-learn, and NumExpr

The packaging of MKL with redistributable binaries in Anaconda for easy access to the MKL runtime library.

Python bindings to the low level MKL service functions, which allow for the modification of the number of threads being used during runtime.

Existing MKL licenses can be viewed and removed with the
graphical Anaconda Navigator license manager or manually with your
operating system. For more information please see the
License installation page.

Anaconda now also includes a small utility package called
mkl-service which provides a Python interface to some
useful MKL functions that are declared in mkl_service.h, such as setting
the number of threads to use.

MKL takes roughly 100MB and some use cases do not need it, so users can opt out
of MKL and instead use OpenBLAS for Linux or the
native Accelerate Framework for MacOSX. To opt out, run condainstallnomkl
and then use condainstall to install packages that would normally include
MKL or depend on packages that include MKL, such as scipy, numpy, and
pandas. Conda will install the non-MKL versions of these packages together
with their dependencies. If you are using OS X or Linux, have already installed
these packages or already installed all of Anaconda, and wish to switch away
from MKL, use the command condainstallnomklnumpyscipyscikit-learnnumexpr
followed by condaremovemklmkl-service.

Because past versions of Anaconda did not include MKL linked binaries by default,
some users who have used condaupdate--all may see an MKL Trial warning or
a license expiration error, even though MKL linked packages are now free and
installed by default. A license expiration error message may read, “You cannot
run MKL without a license any longer.”

To resolve this, set your installation to use the mkl-linked libraries that do not require a license: